What mileage does your slant six powered ride get?

[Garys72Duster]

I fill my tank to the brim and drive it as daily as I normally do daily, after two days I go back and fill it back up to the brim and take a look at the amount of gas it to to fill it back to the brim, take a mileage reading and do the math, then if I take a trip 200 miles or a little less, do the same, about the closest I can get.

That' prob the best way to do it. For example, I filled my car up, drove 176 miles, filled it again. Took 5.9 gallons to fill it back to the top of the tank. So I take 176 miles, divided by 5.9=29.8 MPG. Then you can keep a running log, each time you fill it, then average all readings.

 

[a12]

I call bullshit on any slant six automatic getting over 20mpg, especially in a 67 and up a body either you have a bad gas gauge, or speedos off. Best mileage would be with early a bodies with an overdrive no power anything, probably at best 22mpg. Maybe better with a 198 or 170. For me the biggest gain in fuel mileage was converting over to a 4 speed with a 225 went from 17mpg to 20mpg. I dont count my mileage from my speedo, or gauge. I carry two 1 gallon tanks of gas drive until i run out and count my mileage on gps. I bet if you guys did this you will actually see what mileage you get not just guessing and rounding.

 

[moparblood]

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you can call it whatever you want. it still is what it is. its Not that hard to believe. why bs about it? as i stated NOT all motors are the same!

 

[Garys72Duster]

I got 11 MPG with my 70 Dart, 440, driving from LA to Denver. All Hwy. NO KIDDING! Found out the primary power valve on my 750 Holley was blown, and always open.
I was wondering why I had a trail of black smoke coming out the back. True story.

 

[doc540]

I call bullshit on any slant six automatic getting over 20mpg, especially in a 67 and up a body either you have a bad gas gauge, or speedos off. Best mileage would be with early a bodies with an overdrive no power anything, probably at best 22mpg. Maybe better with a 198 or 170. For me the biggest gain in fuel mileage was converting over to a 4 speed with a 225 went from 17mpg to 20mpg. I dont count my mileage from my speedo, or gauge. I carry two 1 gallon tanks of gas drive until i run out and count my mileage on gps. I bet if you guys did this you will actually see what mileage you get not just guessing and rounding.

Are you a wagering man?

 

[Slantsix64]

Are you a wagering man?

View attachment 1715271534

Yup you bet I am.

 

[Ddaddy]

I daily drive a 68 dart with a slant six and an 833 od. I get 14 in town and 17 on the highway.

I have electronic ignition on it and I could probably get better mileage if I was easier on it but I tend to be a lead foot and don't let a lot of people pass me.

That sounds about right. I’ve owned and regularly driven probably a dozen slant 6 cars in my life and never saw much better than around 18 mpg on the highway. Of course, none of those had an OD transmission.

If I could average 17 mpg in mixed driving, I thought it was good enough since I always tuned for power...not mpg.

 

[RustyRatRod]

That' prob the best way to do it. For example, I filled my car up, drove 176 miles, filled it again. Took 5.9 gallons to fill it back to the top of the tank. So I take 176 miles, divided by 5.9=29.8 MPG. Then you can keep a running log, each time you fill it, then average all readings.

That is exactly right. The more fill ups in your average, the more accurate your average. Also, you need about a "half and half" mix of city and highway driving to be even more accurate.

 

[318willrun]

I like to at least go over 200 miles on the tank, but the more the merrier. If I can fill up at the same pump, that's even better. A 3 tank average is even better. Gas mileage is rated city/highway. Also, lots of hills play a part. This being said.....

• I had a '74 Dodge truck, slant six 1 bbl 4 speed. 24 mpg going back and forth to work at 55 mph. Yes, the odometer was accurate. I commuted 34 miles one way.
• My dad had a '68 valiant with a slant that got 28 mpg on the interstate. Like it or not, believe it or not, it's what it got. He drove from Colo to Wheatland, Wyoming to work. We also took it from Colo to Washington.
• We've had some that stunk at gas mileage too, because something was wrong with them.

 

[doc540]

Yup you bet I am.

Just made the gear change along with a new intake/header gasket.

A tad lean, but the mileage run was purposed for an accurate check.

Filled up at the same pump leaving and on return.

1961 Lancer
A904
2.73 rear
Pertronix ignition
Head work, mild cam, Clifford intake and shorty headers, Holley 390
91 VP non-ethanol

24mpg highway at 65mph

 

[Princess Valiant]

That sounds about right. I’ve owned and regularly driven probably a dozen slant 6 cars in my life and never saw much better than around 18 mpg on the highway. Of course, none of those had an OD transmission.

If I could average 17 mpg in mixed driving, I thought it was good enough since I always tuned for power...not mpg.

The OD isn't really what people think it is. The last gear is not a very responsive gear to the throttle so you end up down shifting a lot. Even on the interstate I find the last gear isn't enough to pass someone. I am always down shifting for more power so it defeats the point of the OD and ends up being more like a standard three speed.

I suppose the OD works better if you kept at a constant 55 but trying to keep it between 78 and 88 mph in a 75 zone requires a lot of downshifting to 1:1 just to keep up with traffic.

 

[Princess Valiant]

Just made the gear change along with a new intake/header gasket.

A tad lean, but the mileage run was purposed for an accurate check.

Filled up at the same pump leaving and on return.

1961 Lancer
A904
2.73 rear
Pertronix ignition
Head work, mild cam, Clifford intake and shorty headers, Holley 390
91 VP non-ethanol

24mpg highway at 65mph

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Where did you get the air cleaner decal, that's badass

 

[Garys72Duster]

Where did you get the air cleaner decal, that's badass

And is that engine paint Chryslers Corporate Blue, used on early 70s motors? Very nice looking motor!

 

[doc540]

Thanks

Daughter had the decal made for Father's Day gift. (she's a graphic designer, but just modified a decal I found on the net)

Engine color is "kind of" a Petty blue that a local powder coat company had in stock. They said other MoPar owners had used it on their engines.

Interior is blue and black, so...

 

[66fs]

Stone cold stock 1964 Valiant V-100. 1964 Mobile Economy Run from LA to NYC, average 23.0851 mpg over 3,243.8 miles. Combination city and Highway. Easily mid to upper 20's if not 30+ mpg cruising steady on a flatish highway.

https://www.hsmichigan.org/wp-content/uploads/2012/08/Mobil

 

[moparblood]

Stone cold stock 1964 Valiant V-100. 1964 Mobile Economy Run from LA to NYC, average 23.0851 mpg over 3,243.8 miles. Combination city and Highway. Easily mid to upper 20's if not 30+ mpg cruising steady on a flatish highway.

https://www.hsmichigan.org/wp-content/uploads/2012/08/Mobil

the OD gear is more like a 5 speed with No 4th. when doing these averages, its at 55mph should be No or No less. when you increase the HP on a motor, you most likely substitute mpg's. or go over 55 mph.

 

[toolmanmike]

Just made the gear change along with a new intake/header gasket.

A tad lean, but the mileage run was purposed for an accurate check.

Filled up at the same pump leaving and on return.

1961 Lancer
A904
2.73 rear
Pertronix ignition
Head work, mild cam, Clifford intake and shorty headers, Holley 390
91 VP non-ethanol

24mpg highway at 65mph

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Or make your own.

 

[a12]

up to 24 is believable, but after that

 

[RustyRatRod]

I wonder what difference a T5 transmission might make? Food for thought.

 

[RustyRatRod]

Just made the gear change along with a new intake/header gasket.

A tad lean, but the mileage run was purposed for an accurate check.

Filled up at the same pump leaving and on return.

1961 Lancer
A904
2.73 rear
Pertronix ignition
Head work, mild cam, Clifford intake and shorty headers, Holley 390
91 VP non-ethanol

24mpg highway at 65mph

View attachment 1715271648

View attachment 1715271650

I agree with the others. That does look real nice.

 

[66fs]

the OD gear is more like a 5 speed with No 4th. when doing these averages, its at 55mph should be No or No less. when you increase the HP on a motor, you most likely substitute mpg's. or go over 55 mph.

No O/D not mine, documented from 1964. If you read the article, it describes conditions, and that these were off the lot cars with strict fueling and non tampering policy. LOL that you guys can't believe some of the stuff that some of our members have achieved. Mine by efficiency as I was building for power, not fuel economy.

 

[Charrlie_S]

No O/D not mine, documented from 1964. If you read the article, it describes conditions, and that these were off the lot cars with strict fueling and non tampering policy. LOL that you guys can't believe some of the stuff that some of our members have achieved. Mine by efficiency as I was building for power, not fuel economy.

I was building for fuel economy, and my engine is not stock. So I don't understand why some don't believe that I can get upper 20's MPG

 

[Slantsix64]

Just made the gear change along with a new intake/header gasket.

A tad lean, but the mileage run was purposed for an accurate check.

Filled up at the same pump leaving and on return.

1961 Lancer
A904
2.73 rear
Pertronix ignition
Head work, mild cam, Clifford intake and shorty headers, Holley 390
91 VP non-ethanol

24mpg highway at 65mph

View attachment 1715271648

View attachment 1715271650

What set up are you running in that 390? wheres your timing at. Also that is a badass air cleaner decal

 

[doc540]

What set up are you running in that 390? wheres your timing at. Also that is a badass air cleaner decal

Thanks

I'll have to ask my old friend and mechanic what jets we ended up with.
And we just set the timing by ear and feel.

Got it running like a Singer right now.

 

[KosmicKuda]

Stone cold stock 1964 Valiant V-100. 1964 Mobile Economy Run from LA to NYC, average 23.0851 mpg over 3,243.8 miles. Combination city and Highway. Easily mid to upper 20's if not 30+ mpg cruising steady on a flatish highway.

https://www.hsmichigan.org/wp-content/uploads/2012/08/Mobil

That's what I'm talking about! Chrysler cars always kicked *** in the Mobil economy runs.

Of course, if you know anything about Chrysler engineers you KNOW they studied, tested, and honed their techniques. Give them a challenge and they came out in top. From what I remember they accelerated to the speed limit quickly but not enough to waste gas. IIRC, there was an official observer in the cars to check for cheating.

But at least one time they put a ball bearing in the ash tray and used it as an inclinometer.
Our old cars had, and still have, an advantage due to those anal-retentive engineers.